What is external beam radiation therapy?

Radiation therapy, also called radiotherapy, is the branch of medicine that deals with the treatment of cancer by delivering high-energy beams directly to a tumor, or intended target. It is a treatment option for multiple types of cancer, and approximately 50 percent1 of cancer patients globally received radiation therapy as part of their treatment plan.

1Baskar, R., & Itahana, K. (2017, January 1). Radiation therapy and cancer control in developing countries: Can we save more lives?. National Library of Medicine. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5278654/)
External Beam Radiation Therapy

How does it work?

External beam radiation therapy—sometimes called radiotherapy or “RT”—has been used to treat cancer for over a century. Today, radiation therapy has evolved to deliver targeted treatments with incredible precision, using the latest technologies.

  • The cells in your body normally grow and divide to form new cells. Cancer cells grow and divide faster than most normal cells.
  • Radiation therapy aims waves, such as x-rays, or high-energy particles, such as electrons or protons, at cancer cells to damage their DNA.
  • Cancer cells with damaged DNA may not be able to divide and proliferate and the cells are then programmed to die.
  • It may be used as the primary cancer treatment or combined with other treatment options. It may also be used to reduce symptoms caused by advanced cancer.
Docter with patient
External Beam Radiation Therapy

Stereotactic treatments

Radiosurgery, or stereotactic radiosurgery (SRS), is a form of external beam radiation therapy that uses highly-focused beams to deliver larger doses of radiation in fewer treatments. Radiosurgery is used to treat tumors in the central nervous system (CNS). The number of radiosurgery treatments required typically range from a single treatment to about five treatments. Your radiation oncologist may recommend radiosurgery as an alternative to conventional surgery, especially when the tumor is inaccessible for open surgery, or if the operation is considered high-risk.

Stereotactic body radiation therapy (SBRT)/stereotactic ablative radiotherapy (SABR) is a form of external beam radiation therapy that uses highly-focused beams to deliver larger doses of radiation in fewer treatments. SBRT/SABR is used to treat tumors in the body, outside of the CNS. The number of SBRT/SABR treatments required typically range from a single treatment to about five treatments.

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External Beam Radiation Therapy

Treatment sessions

If radiation therapy is recommended as part of your treatment, here’s what you can expect:

  • Many patients find that their radiation therapy sessions have a minimal effect on their daily schedules.
  • Treatment sessions are typically given on an outpatient basis, meaning no hospital stay is required.
  • Treatment sessions can range from as little as 15 minutes to several hours, depending upon the technique.
External Beam Radiation Therapy

Possible side effects

In general, side effects depend on a number of factors including region of the body being treated, radiation dose, treatment technique, cancer type, and stage of cancer. Your care team will talk to you about what you should expect during and after your treatment. They will monitor you throughout your treatment journey for any side effects.

External Beam Radiation Therapy

Treatment team

Radiation treatment is administered to you by a team of highly qualified healthcare professionals who specialize in treating cancer. Some of the typical members of the team are listed below; depending on your particular case, other specialists may be asked to join the team.

Medical Team
External Beam Radiation Therapy

Common misperceptions about radiation therapy

  • External beam radiation therapy does not make you radioactive.
  • You can’t see, hear, feel, or smell the radiation beam during treatment.
  • Most patients can continue daily activities, despite side effects such as fatigue.
  • Generally, hospitalization is not required during the course of radiation therapy.

Have questions about external beam radiation therapy? We have helpful answers for you.

Find answers to common questions on our FAQ page.